The present invention relates to photographic film units of the instant-processing type, and more specifically to such units which can be handled individually in daylight without fogging.
Previous instant-processing film units have taken a wide variety of forms, two of which are discussed below. One, frequently referred to as a 4.times.5 unit, because of the print dimensions produced by present commercial products, is depicted in U.S. Pat. No. 3,053,160, issued on Sept. 11, 1962. This first type also may be referred to as a post-registered, peel-apart film unit with reference to the initial and final positions of its respective elements. Another is depicted in U.S. Pat. No. 4,042,395, issued on Aug. 16, 1977 (application Ser. No. 572,541, entitled INTEGRAL FILM UNIT, and filed in the names of Frederick F. Tone et al. on Apr. 28, 1975.) This second type frequently is referred to as a pre-registered, integral film unit, again with reference to the positions of its elements.
Both of the above forms include a photosensitive element, a second sheet, and a pod containing processing composition. The photosensitive element has one or more layers of light-sensitive material for recording a latent image that is processable to establish a visible image. The second sheet is adapted to facilitate distribution of the processing composition over the photosensitive element for initiating such processing. It also may act as a support for the final visible image, but in some integral film units, such as the one described in the above-referenced application, the final image remains with the photosensitive element. In operation, the film units are moved through a processing device, such as a pair of pressure rollers, which ruptures the pod and distributes the composition in a layer of appropriate thickness between the photosensitive element and second sheet. The distributed composition then permeates the layers to process the latent image and establish the visible image.
In the 4.times.5 or post-registered, peel-apart type of film unit, the second sheet is separated from the photosensitive element to permit exposure of the element, then brought into registered relationship with the element for processing, and finally separated from the element to view the final print. The term "post-registered" identifies the feature requiring registration after exposure, while the term "peel-apart" refers to the removal of the second sheet from the photosensitive element in order to view the final print.
In the second or preregistered, integral type of film unit, the photosensitive element and second sheet are registered prior to exposure, preferably at the time of manufacture, and remain in substantially the same relative positions during and after exposure and processing. Ordinarily, the second sheet is transparent to permit exposure of the photosensitive element therethrough, and the element and sheet remain permanently attached to each other in the final print.
Further pertinent features of the abovementioned types of film units relate to their handling in daylight. The 4.times.5 unit is adapted to be handled individually in daylight both before and after exposure. This is facilitated by an opaque envelope which surrounds the photosensitive element and second sheet until the unit is loaded in appropriate exposing apparatus. Then the envelope is removed to permit exposure of the photosensitive element. After exposure, the envelope is returned to its original position which registers the second sheet over the element and again provides a light-tight environment. The envelope is removed after processing, and the second sheet is peeled-off, as described above, to reveal the final print.
Previous integral film units have not been designed for individual daylight handling prior to exposure. Instead, they are supplied in light-tight packs for loading into the corresponding apparatus. After exposure, however, the film units typically are ejected immediately from the camera, and processing is completed in daylight. This is permitted by providing an opaque layer in the photosensitive element on one side of the light-sensitive layers, and by adding an opacifier to the processing composition. When the opaque composition is distributed over the sensitive layers, it cooperates with the opaque layer to shield the sensitive layers from light. The final image then diffuses through one or the other of the opaque layers (the original layer or the distributed composition), where it is revealed for viewing.
Although previously known film units, such as those described above, apparently operate satisfactorily for their intended purpose, none offer the desired convenience for instant-processing film units that can be handled in daylight on an individual basis both before and after exposure. The 4.times.5 type described above requires rather complex manipulation of the opaque envelope. Moreover, even after removal of the envelope, the final print must be stripped from the photosensitive element. The film units are intricate in construction and difficult to manufacture, generate considerable waste in use, and require relatively complex utilizing apparatus which resists automation. While integral film units do not suffer from these problems, they have not been suitable for pre-exposure daylight handling on an individual or one-shot basis.